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Concave cover strip

Fitting the truss rod

Fitting a truss rod into a one-piece neck

On one-piece necks (without separately-made fingerboard) the truss rod has to be installed from the back (1). For this purpose the rails used for routing have to be made convex. Instead of taping the rails onto the neck blank the blank can also be placed into a jig (2,3) fitted with a block for stopping the router. Several passes will be required to cut the channel to the desired depth.

Guitars which are to have a back-mounted truss rod and a head-end adjustment nut require the drilling of a hole that connects the peghead with the truss rod channel. How to make a Fender-style peghead, which is necessary for this purpose, will be explained on page 149. Making a reliable jig for this quite difficult drilling job can be a lot of work. I tried to keep things simple and had good results, too. Draw the depth of the channel and the necessary drilling angle onto the edge of the neck blank. Fasten the power drill in a holder, inserting a shim (4) under it so that it ends up lying at an angle of about 3 degrees. Bring the neck blank up to the required height by putting some boards under it (4). The drill bits used have to be at least 30cm (1 feet) long.

Skunk stripe

The cover strip fitted over a truss rod installed from the back is often made from contrasting wood. That's why it was given its graphic name after the skin pattern of an animal called skunk.

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Shim

Start with a bit that is equal in diameter to the adjustment nut. ow deep you have to drill depends upon the length of the nut plus washer. The adjustment nut may also protrude slightly. To make the bit really bite into the wood I pre-drill a little bit by hand before turning to the electric drill. Push the neck blank into the drill by moving it along a fence. Then mount a 6mm (1/4") bit and drill right through to the truss rod channel on the back. A mark made on the bit before drilling indicates when the right depth has been reached.

Cover the channel in which the back-mounted, and therefore convex-curved, truss rod lies with a strip of hardwood timber (1). For optical reasons it is advisable to use a strip of dark-colored wood for this purpose. Cut out the strip slightly wider and thicker than needed and then carefully plane or rout it down so that it can be pressed into the channel and fits there tight. Use a file to cut one of its ends flush with the curved end of the channel. Getting the size of the cover strip right is essential, in particular when using it to cover a back-side channel. So if you discover your strip doesn't fit precisely, you had better make a new one which is exactly the right size; a cover strip that is too wide can break the neck blank when the strip is glued in, while one that is too small, and perhaps also glued in badly, may be pressed out later by the force of the truss rod. This is less of a problem when the cover strip is fitted from the front as in that case the strain is spread all over the glued-on fingerboard.

Fitting a two-way twin truss rod

A two-way twin rod does not require a wooden fillet under the fingerboard as the straight channel, which is made 11mm (7/16") deep and 6mm (7/32") wide, is covered by the fingerboard. Due to the large gluing area and the thickness of the fingerboard there is no danger of it being pressed away from the truss rod. The truss rod shown in picture 5 comes from Stewart-MacDonald and is called “Hot Rod” (a similar truss rod is also available from LMI).

In picture 5 you can see me fitting a “Hot Rod” from the back, for which I needed a fillet (a so-called “skunk stripe”). Because it is fitted from the back, the

truss rod channel is made 16mm (5/8") deep, so 3mm (1/8") of wood will be left under the fingerboard. As suggested in the fitting instructions that came with this truss rod, I embedded the thread blocks in silicone.

Two-way compression rod

For the installation of a two-way compression rod a straight channel and two short cross channels for the anchor nuts are needed. The headless neck shown in picture 4 is intended for a headless bass. The hole for the adjustment nut was drilled with several bits, starting with a small-diameter one, followed by one 0.5mm greater in diameter, and so on. Alternatively, you could also choose the easier approach of temporarily placing the fillet strip into the channel and to drill only once, using the right size of bit straight away.

Cut out two anchor nut cavities from the fillet. Make sure that the truss rod can be turned after it has been installed.